Malignant hyperthermia facts*

Malignant hyperthermia is a severe reaction to particular drugs that are often used during general anesthesia for surgery.

Malignant hyperthermia occurs in 1 in 5,000 to 50,000 instances in which people are given anesthetic gases.

Muscle rigidity, breakdown of muscle fibers (rhabdomyolysis), a high fever, increased acid levels in the blood and other tissues (acidosis), and a rapid heart rate are some of the effects of this potentially life-threatening condition.

Researchers have described at least six forms of malignant hyperthermia susceptibility, which are caused by mutations in different genes. For example, variations of the CACNA1S and RYR1 genes increase the risk of developing malignant hyperthermia.

Malignant hyperthermia susceptibility is inherited in an autosomal dominant manner (which means that one copy of the altered gene in each cell is sufficient to increase the risk of the condition).

What is malignant hyperthermia?

Malignant hyperthermia is a severe reaction to particular drugs that are
often used during surgery and other invasive procedures. Specifically, this
reaction occurs in response to some anesthetic gases, which are used to block
the sensation of pain, and with a muscle relaxant that is used to temporarily
paralyze a person during a surgical procedure. If given these drugs, people at
risk for malignant hyperthermia may experience muscle rigidity, breakdown of
muscle fibers (rhabdomyolysis), a high fever, increased acid levels in the blood
and other tissues (acidosis), and a rapid heart rate. Without prompt treatment,
the complications of malignant hyperthermia can be life-threatening.

People at increased risk for this disorder are said to have malignant
hyperthermia susceptibility. Affected individuals may never know they have the
condition unless they undergo testing or have a severe reaction to anesthesia
during a surgical procedure. While this condition often occurs in people without
other serious medical problems, certain inherited muscle diseases (including
central core disease and multiminicore disease) are associated with malignant
hyperthermia susceptibility.